ARM: GIC: Convert GIC library to use the IO relaxed operations

The GIC register accesses today make use of readl()/writel()
which prove to be very expensive when used along with mandatory
barriers. This mandatory barriers also introduces an un-necessary
and expensive l2x0_sync() operation. On Cortex-A9 MP cores, GIC
IO accesses from CPU are direct and doesn't go through L2X0 write
buffer.

A DSB before writel_relaxed() in gic_raise_softirq() is added to be
compliant with the Barrier Litmus document - the mailbox scenario.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>

1 files changed, 30 insertions, 24 deletions

diff --git a/arch/arm/common/gic.c b/arch/arm/common/gic.c
index e9c2ff83909b..4ddd0a6ac7ff 100644
--- a/arch/arm/common/gic.c
+++ b/arch/arm/common/gic.c
@@ -89,7 +89,7 @@ static void gic_mask_irq(struct irq_data *d)
         u32 mask = 1 << (d->irq % 32);
 
         spin_lock(&irq_controller_lock);
-        writel(mask, gic_dist_base(d) + GIC_DIST_ENABLE_CLEAR + (gic_irq(d) / 32) * 4);
+        writel_relaxed(mask, gic_dist_base(d) + GIC_DIST_ENABLE_CLEAR + (gic_irq(d) / 32) * 4);
         if (gic_arch_extn.irq_mask)
                 gic_arch_extn.irq_mask(d);
         spin_unlock(&irq_controller_lock);
@@ -102,7 +102,7 @@ static void gic_unmask_irq(struct irq_data *d)
         spin_lock(&irq_controller_lock);
         if (gic_arch_extn.irq_unmask)
                 gic_arch_extn.irq_unmask(d);
-        writel(mask, gic_dist_base(d) + GIC_DIST_ENABLE_SET + (gic_irq(d) / 32) * 4);
+        writel_relaxed(mask, gic_dist_base(d) + GIC_DIST_ENABLE_SET + (gic_irq(d) / 32) * 4);
         spin_unlock(&irq_controller_lock);
 }
 
@@ -114,7 +114,7 @@ static void gic_eoi_irq(struct irq_data *d)
                 spin_unlock(&irq_controller_lock);
         }
 
-        writel(gic_irq(d), gic_cpu_base(d) + GIC_CPU_EOI);
+        writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_EOI);
 }
 
 static int gic_set_type(struct irq_data *d, unsigned int type)
@@ -140,7 +140,7 @@ static int gic_set_type(struct irq_data *d, unsigned int type)
         if (gic_arch_extn.irq_set_type)
                 gic_arch_extn.irq_set_type(d, type);
 
-        val = readl(base + GIC_DIST_CONFIG + confoff);
+        val = readl_relaxed(base + GIC_DIST_CONFIG + confoff);
         if (type == IRQ_TYPE_LEVEL_HIGH)
                 val &= ~confmask;
         else if (type == IRQ_TYPE_EDGE_RISING)
@@ -150,15 +150,15 @@ static int gic_set_type(struct irq_data *d, unsigned int type)
          * As recommended by the spec, disable the interrupt before changing
          * the configuration
          */
-        if (readl(base + GIC_DIST_ENABLE_SET + enableoff) & enablemask) {
-                writel(enablemask, base + GIC_DIST_ENABLE_CLEAR + enableoff);
+        if (readl_relaxed(base + GIC_DIST_ENABLE_SET + enableoff) & enablemask) {
+                writel_relaxed(enablemask, base + GIC_DIST_ENABLE_CLEAR + enableoff);
                 enabled = true;
         }
 
-        writel(val, base + GIC_DIST_CONFIG + confoff);
+        writel_relaxed(val, base + GIC_DIST_CONFIG + confoff);
 
         if (enabled)
-                writel(enablemask, base + GIC_DIST_ENABLE_SET + enableoff);
+                writel_relaxed(enablemask, base + GIC_DIST_ENABLE_SET + enableoff);
 
         spin_unlock(&irq_controller_lock);
 
@@ -190,8 +190,8 @@ static int gic_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
 
         spin_lock(&irq_controller_lock);
         d->node = cpu;
-        val = readl(reg) & ~mask;
-        writel(val | bit, reg);
+        val = readl_relaxed(reg) & ~mask;
+        writel_relaxed(val | bit, reg);
         spin_unlock(&irq_controller_lock);
 
         return 0;
@@ -223,7 +223,7 @@ static void gic_handle_cascade_irq(unsigned int irq, struct irq_desc *desc)
         chained_irq_enter(chip, desc);
 
         spin_lock(&irq_controller_lock);
-        status = readl(chip_data->cpu_base + GIC_CPU_INTACK);
+        status = readl_relaxed(chip_data->cpu_base + GIC_CPU_INTACK);
         spin_unlock(&irq_controller_lock);
 
         gic_irq = (status & 0x3ff);
@@ -272,13 +272,13 @@ static void __init gic_dist_init(struct gic_chip_data *gic,
         cpumask |= cpumask << 8;
         cpumask |= cpumask << 16;
 
-        writel(0, base + GIC_DIST_CTRL);
+        writel_relaxed(0, base + GIC_DIST_CTRL);
 
         /*
          * Find out how many interrupts are supported.
          * The GIC only supports up to 1020 interrupt sources.
          */
-        gic_irqs = readl(base + GIC_DIST_CTR) & 0x1f;
+        gic_irqs = readl_relaxed(base + GIC_DIST_CTR) & 0x1f;
         gic_irqs = (gic_irqs + 1) * 32;
         if (gic_irqs > 1020)
                 gic_irqs = 1020;
@@ -287,26 +287,26 @@ static void __init gic_dist_init(struct gic_chip_data *gic,
          * Set all global interrupts to be level triggered, active low.
          */
         for (i = 32; i < gic_irqs; i += 16)
-                writel(0, base + GIC_DIST_CONFIG + i * 4 / 16);
+                writel_relaxed(0, base + GIC_DIST_CONFIG + i * 4 / 16);
 
         /*
          * Set all global interrupts to this CPU only.
          */
         for (i = 32; i < gic_irqs; i += 4)
-                writel(cpumask, base + GIC_DIST_TARGET + i * 4 / 4);
+                writel_relaxed(cpumask, base + GIC_DIST_TARGET + i * 4 / 4);
 
         /*
          * Set priority on all global interrupts.
          */
         for (i = 32; i < gic_irqs; i += 4)
-                writel(0xa0a0a0a0, base + GIC_DIST_PRI + i * 4 / 4);
+                writel_relaxed(0xa0a0a0a0, base + GIC_DIST_PRI + i * 4 / 4);
 
         /*
          * Disable all interrupts.  Leave the PPI and SGIs alone
          * as these enables are banked registers.
          */
         for (i = 32; i < gic_irqs; i += 32)
-                writel(0xffffffff, base + GIC_DIST_ENABLE_CLEAR + i * 4 / 32);
+                writel_relaxed(0xffffffff, base + GIC_DIST_ENABLE_CLEAR + i * 4 / 32);
 
         /*
          * Limit number of interrupts registered to the platform maximum
@@ -324,7 +324,7 @@ static void __init gic_dist_init(struct gic_chip_data *gic,
                 set_irq_flags(i, IRQF_VALID | IRQF_PROBE);
         }
 
-        writel(1, base + GIC_DIST_CTRL);
+        writel_relaxed(1, base + GIC_DIST_CTRL);
 }
 
 static void __cpuinit gic_cpu_init(struct gic_chip_data *gic)
@@ -337,17 +337,17 @@ static void __cpuinit gic_cpu_init(struct gic_chip_data *gic)
          * Deal with the banked PPI and SGI interrupts - disable all
          * PPI interrupts, ensure all SGI interrupts are enabled.
          */
-        writel(0xffff0000, dist_base + GIC_DIST_ENABLE_CLEAR);
-        writel(0x0000ffff, dist_base + GIC_DIST_ENABLE_SET);
+        writel_relaxed(0xffff0000, dist_base + GIC_DIST_ENABLE_CLEAR);
+        writel_relaxed(0x0000ffff, dist_base + GIC_DIST_ENABLE_SET);
 
         /*
          * Set priority on PPI and SGI interrupts
          */
         for (i = 0; i < 32; i += 4)
-                writel(0xa0a0a0a0, dist_base + GIC_DIST_PRI + i * 4 / 4);
+                writel_relaxed(0xa0a0a0a0, dist_base + GIC_DIST_PRI + i * 4 / 4);
 
-        writel(0xf0, base + GIC_CPU_PRIMASK);
-        writel(1, base + GIC_CPU_CTRL);
+        writel_relaxed(0xf0, base + GIC_CPU_PRIMASK);
+        writel_relaxed(1, base + GIC_CPU_CTRL);
 }
 
 void __init gic_init(unsigned int gic_nr, unsigned int irq_start,
@@ -391,7 +391,13 @@ void gic_raise_softirq(const struct cpumask *mask, unsigned int irq)
 {
         unsigned long map = *cpus_addr(*mask);
 
+        /*
+         * Ensure that stores to Normal memory are visible to the
+         * other CPUs before issuing the IPI.
+         */
+        dsb();
+
         /* this always happens on GIC0 */
-        writel(map << 16 | irq, gic_data[0].dist_base + GIC_DIST_SOFTINT);
+        writel_relaxed(map << 16 | irq, gic_data[0].dist_base + GIC_DIST_SOFTINT);
 }
 #endif